1. Field of the Invention
The invention relates to a liquid crystal display device characterized in a structure of connection between electrode driving ICs mounted on substrates and electrodes such as scanning electrodes, signal electrodes, and the like which are provided on the substrates.
2. Description of the Related Art
Super twisted nematic (STN) liquid crystal display devices are employed most widely for small display units such as cellular phones and the like. Since a decrease in size of an outer case and an increase in size of an image display portion are simultaneously demanded in a cellular phone in particular, it is necessary to devise the structure of the liquid crystal display device and the arrangement of electrode driving ICs. Recently, the number of pixels increases to perform display in colors and gradations as well, and thus a small liquid crystal panel for a cellular phone is offered, in which a scanning electrode driving IC and a signal electrode driving IC are arranged on two sides respectively similarly to the arrangement of the electrode driving ICs in a large liquid crystal panel. Such a structure, however, is not desired in terms of design because of broken symmetry of the liquid crystal panel.
Therefore, a configuration using a one-chip electrode driving IC in which a scanning electrode driving circuit, a signal electrode driving circuit, an image memory, and a display control circuit are formed in one electrode driving IC, or a configuration in which all the driving circuits are mounted on one side of one substrate, is begun to be used.
An arrangement of members and a wiring state in a conventional liquid crystal display device using a one-chip electrode driving IC are explained here using FIG. 18 to FIG. 21. FIG. 18 is a plan view of the liquid crystal display device, FIG. 19 is a side view of the same as viewed from a direction of an arrow A in FIG. 18, FIG. 20 is a plan view showing an arrangement of electrodes in the liquid crystal display device, and FIG. 21 is a view for explaining an arrangement of connecting wirings connected to scanning electrodes in the liquid crystal display device. In these drawings, the illustration of optical members such as a polarizer, a reflector and the like is omitted.
In this liquid crystal display device, an electrode driving IC 62 is mounted on an upper substrate 61 which is made of glass. A method, in which the electrode driving IC is mounted on the substrate as described above, is often employed. (It is called chip-on-board. With a glass substrate, it is called chip-on-glass and hereinafter referred to as COG.) As shown in FIG. 18 and FIG. 19, the electrode driving IC 62, a lower substrate 63 which is made of glass, and a connecting film circuit (called a flexible printed circuit, and hereinafter referred to as an FPC) 64 are adhered to a back face of the upper substrate 61. Among them, the upper substrate 61 and the lower substrate 63 are adhered to each other with a sealing portion 69 and hold a liquid crystal layer sandwiched therebetween.
On these substrates, electrodes are formed on respective faces on the liquid crystal layer sides. In FIG. 20, solid lines show the electrodes formed on (the back face of) the upper substrate 61, and phantom lines show the electrodes formed on the lower substrate 63. Broken lines represent repetition of respective components.
As shown in FIG. 20, scanning electrodes 65 are formed of ITO (indium tin oxide) on the lower substrate 63. Further, signal electrodes 66, wirings 68 for connecting them to the FPC 64, and connecting wirings 67 for connecting the scanning electrodes 65 and electrode driving terminals of the electrode driving IC 62 are formed of ITO on the back face of the upper substrate 61. Then portions where the scanning electrodes 65 and the signal electrodes 66 overlap (oppose) each other in a plan view become individual pixels, and a region where these pixels perform effective display based on image data becomes an image display portion 612 shown by the phantom line.
A face with terminals of the electrode driving IC 62 and the connecting wirings on the upper substrate 61 are electrically connected to each other with an anisotropic conductive film (hereinafter, referred to as an ACF) sandwiched therebetween. Similarly, not shown wirings on the FPC 64 and the wirings 68 on the upper substrate 61 are also connected to each other by an ACF within connecting regions 611.
FIG. 21 shows only members associated with the connection between the scanning electrodes 65 and the electrode driving IC 62. As shown in this drawing, the scanning electrodes 65 and the connecting wirings 67 are connected to each other through the sealing portion 69 at connecting regions 610. The sealing portion 69, in which conductive particles are mixed here, is an anisotropic conductive sealing portion which makes conduction only in a direction perpendicular to the substrates 61 and 63.
Assuming that the place where the electrode driving IC 62 is mounted is the upper side of the image display portion 612, the scanning electrode driving terminals on the left-hand side of the electrode driving IC 62 are connected to the scanning electrodes 65 arranged at the upper half of the image display portion 612, and the scanning electrode driving terminals on the right-hand side are connected to the scanning electrodes 65 arranged at the lower half of the image display portion 612.
Further, the connecting wirings 67 for the scanning electrode driving terminals extending from the lower side of the electrode driving IC 62 in FIG. 21 are connected to the scanning electrodes 65 in the connecting regions 610 which are arranged at the upper side of the sealing portion 69. The connecting wirings 67 extending from the upper side thereof are connected to the scanning electrodes 65 in the connecting regions 610 which are arranged at the left-hand side (or the right-hand side) of the sealing portion 69.
In the case of a small number of display digits provided as in an early-type liquid crystal display panel for a cellular phone, the connecting wirings 67 provided only at the upper side of the image display portion 612 enabled connection between the electrode driving IC 62 and the scanning electrodes 65. In the case of a large number of display digits, however, sufficient region for connection can not be obtained if wirings are drawn only from the upper side of the image display portion, because the pitch of the connecting regions 610 needs to be made larger than the pitch of the connecting wirings 67. Accordingly, as shown in FIG. 19 and FIG. 20, the connecting wirings 67 need to be routed from the left- and right-hand sides of the image display portion 612.
In the liquid crystal display device for a cellular phone, the demand is always to decrease the size of a glass external shape as described above. On the other hand, an increase in display information volume and an increase in the number of scanning electrodes of the liquid crystal display device require widening a region for the connecting wirings, resulting in increased glass external shape. Further, a pair of substrates are bonded together with a sealing material, in which a problem is caused from situation wherein a disregard for the positional relationship between a sealing portion where the sealing material is provided and the region for the connecting wirings might cause a decrease in productivity and display quality.
In other words, when fabricating a liquid crystal display device, a method is used which bonds a pair of large substrates together and cuts out a plurality of liquid crystal display devices therefrom, in which if the connecting wirings are provided outside the sealing portion, the cutting for cutting out the liquid crystal display devices is performed near the connecting wirings. This possibly exerts adverse effects on the connecting wirings such as break lines due to cracks of substrates and foreign substances appearing in the cut portion.
Hence, it is an object of this invention to solve these problems and to realize a small and reliable liquid crystal display device securing a sufficient display information volume. Further, it is another object of this invention to realize a liquid crystal display device having a low cost and an excellent display quality.
To achieve the above objects, this invention is a liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates each provided with electrodes and an electrode driving IC, mounted only at one side of either one of the pair of substrates, for driving the respective electrodes on the pair of substrates, comprising: a sealing portion for bonding the pair of substrates together; and connecting wirings for connecting the electrode driving IC and the electrodes on other substrate, wherein the connecting wirings are arranged between an image display portion provided on an inner side of the sealing portion and the sealing portion, the connecting wirings and the electrodes on the other substrate are electrically connected to each other at connecting regions provided in the sealing portion, and a shielding is provided between the image display portion and the sealing portion.
In such a liquid crystal display device, it is preferable that instead of providing the shielding, the electrode on the other substrate is formed to be thinner at a portion where the connecting wiring opposes the electrode, except the connecting region, than in the image display portion.
Further, it is preferable that the shielding is provided using a low-reflection metal, a black resin, or a member formed by printing.
Further, it is also adoptable that the liquid crystal display device further comprises a polarizer to perform a display using a polarization property of the polarizer, and instead of providing the shielding, the polarizer may be provided in a region other than a region between the image display portion and the sealing portion.
It is also adoptable that instead of providing the shielding, the connecting wiring is provided with a low-reflection chrome layer.
Further, this invention is a liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates each provided with electrodes, an electrode driving IC, mounted only at one side of either one of the pair of substrates, for driving the respective electrodes on the pair of substrates, and a reflection layer, comprising: a sealing portion for bonding the pair of substrates together; and connecting wirings for connecting the electrode driving IC and the electrodes on other substrate, wherein the connecting wirings are arranged between an image display portion provided on an inner side of the sealing portion and the sealing portion, the connecting wirings and the electrodes on the other substrate are electrically connected to each other at connecting regions provided in the sealing portion, and the reflection layer is provided in a region other than a region between the image display portion and the sealing portion.
Alternatively, this invention is a liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates each provided with electrodes and an electrode driving IC, mounted only at one side of either one of the pair of substrates, for driving the respective electrodes on the pair of substrates, comprising: a sealing portion for bonding the pair of substrates together; and connecting wirings for connecting the electrode driving IC and the electrodes on other substrate, wherein the connecting wirings are arranged in the sealing portion, and the connecting wirings and the electrodes on the other substrate are electrically connected to each other at connecting regions provided in the sealing portion.
In each of the above liquid crystal display devices, it is preferable that an external shape of the sealing portion matches an external shape of each side of the pair of substrates except the side where the electrode driving IC is provided.
Alternatively, it is preferable that the respective electrodes on the pair of substrates are signal electrodes and scanning electrodes, and the electrode driving IC comprises at least one signal electrode driving IC for driving the signal electrodes and at least one scanning electrode driving IC for driving the scanning electrodes.
Further, it is preferable that a plurality of the scanning electrode driving ICs are provided and arranged in a manner to put the signal electrode driving IC therebetween.
Further, it is preferable that the scanning electrode driving IC is driven by an oscillation power supply having a period in which a potential thereof changes with time.
Further, it is preferable that the plurality of scanning electrode driving ICs are consisted of two scanning electrode driving ICs, and scanning electrodes connected to one of the scanning electrode driving ICs and scanning electrodes connected to other scanning electrode driving IC are alternately arranged.
The above and other objects, features and advantages of the invention will be apparent from the following detailed description which is to be read in conjunction with the accompanying drawings.